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Posted on Sat, Apr 7, 2012 : 5 a.m.

New recommendation for PSA testing is not the last word

By Ask Dr. K

Harvard Medical School Adviser by the Faculty of Harvard Medical School

Q:

I understand the United States Preventive Services Task Force has released new guidelines for PSA testing for prostate cancer. It's a complicated issue that I find difficult to understand. What's your interpretation?

A:

It's not surprising you're confused; prostate-specific antigen (PSA) testing is a controversial issue. And major news outlets have inadvertently made the issue even more difficult. The New York Times headline announcing the long-awaited United States Preventive Services Task Force (USPSTF) recommendations on PSA testing stated, "U.S. Panel Says No to Prostate Screening for Healthy Men."

The public response was immediate. Some people agreed, some were confused, and some were even angry. The CEO of a prominent prostate cancer advocacy group proclaimed that the USPSTF position "condemns tens of thousands of men to die this year and every year going forward."

PSA testing is a complex issue that requires careful consideration. What the New York Times headline didn't convey is that the USPSTF position is a recommendation, not a command. The task force cannot take away a man's right to have a PSA test, nor would it want to.

Still, the report is important because it points out that screening for early prostate cancer may do more harm than good. That's because although the PSA test itself is simple, interpreting its results is not. And while the test is inexpensive, it can lead to high downstream costs, both in dollars and health.

By now, most men over age 50 in the United States have had a PSA test for prostate cancer, and many have been tested repeatedly. That's no surprise, since Americans have been encouraged to value the early diagnosis of cancer.

But while the appeal of PSA screening is understandable, controversy began almost as soon as the PSA test became popular. Some experts worried that testing might do more harm than good.

The argument for PSA testing is simple. Prostate cancer is the leading internal malignancy in American men. It is also the second-leading cause of cancer death in American men. Early detection of prostate cancer offers the best chance of cure. The PSA blood test is the best currently available way to detect prostate cancer.

That makes PSA screening sound like a no-brainer. But it's not the whole story.

Even the most outspoken critics of routine PSA screening of healthy men agree that testing does detect a large number of early cancers. But skeptics have three reasons for worrying that early diagnosis may not be a good thing.

First, prostate cancer has an extremely variable course. In some cases it's aggressive and lethal. But much more often, it's slow-growing. In other words, many prostate cancers are harmless even if untreated.

Second, the PSA test cannot tell which cancers are likely to be slow-growing and which are aggressive. That means routine screening will detect many tumors that would never cause harm.

Even worse, since a diagnosis of prostate cancer in the United States usually leads to treatment, PSA testing leads to overtreatment. This can lead to significant side effects, with erectile dysfunction heading the list and urinary incontinence in second place. So while PSA testing surely saves some lives, it also produces substantial distress in men who never needed any treatment.

The third issue relates to the test itself. Most American doctors use 4.0 nanograms per milliliter (ng/ml) as a cutoff, accepting results below that as normal and higher values as abnormal. Yet research has documented that many men with PSA scores below the cutoff actually do have prostate cancer, and even more men with scores over this cutoff are free of cancer. That's because benign prostatic hyperplasia (BPH), infections, inflammation and other conditions can boost PSA levels, while many other conditions can lower PSA readings.

The USPSTF has spent years evaluating the pros and cons of PSA screening for prostate cancer. The task force as updated its guideliness as the results of major PSA studies have become available. The new recommendation against routine screening applies to healthy men with no symptoms of prostate cancer and no particular prostate cancer risk factors. Doctors and patients should take the recommendation seriously, but they should also understand that one size does not fit all.

It may be time to redirect some energy and funding to other crucial issues, starting with ways to prevent the disease. We also have a desperate need for good markers to tell if a man is at risk for aggressive prostate cancer, for better ways to distinguish harmless cancers from potential killers, and for research to find treatments that can cure aggressive tumors.

The new USPSTF recommendation is an important evolutionary development, but it is not the last word on PSA testing and it has not done much to quiet the controversy. Still, one thing the most passionate PSA advocates and skeptics can agree on is that America's prostate cancer death toll is far, far too high.